ISC, D2, G4, Racing Logic all look the same but are different colours. The cheap shock is masked by huge spring rates. Also have a look at www.isc-coilovers.com They claim to have lots of R&D and testing, but they came up with some pretty odd solutions for spring rates for skylines, namely the same for 32, 33, 34, 2wd and 4wd, despite the massive difference in handling characteristics and weight distribution.
They are also only bound adjustable and let you choose your own spring rates. I asked the guy a while ago if they revalved the shocks to suit the custom spring rate and they dont, so you will be lucky to get a shock that can control the spring properly.
Personally, I would stay away from all the cheapies.